Communications device, infrastructure equipment, wireless communications network and methods

ABSTRACT

A method is performed in a first infrastructure equipment for a handover of a wireless device from the first infrastructure equipment as a source to a second infrastructure equipment as a target. The method comprises maintaining a mapping between a plurality of packet bearers and a data radio bearer for the wireless device, each of the plurality of packet bearers being configured to provide a specified quality of service, determining that the wireless device should handover from the first infrastructure equipment to the second infrastructure equipment, determining that the second infrastructure equipment does not support the mapping of the plurality of packet bearers to the data radio bearer, and providing an indication of a mapping of the plurality of packet bearers for the second infrastructure equipment after handover to one of a core network equipment and the second infrastructure equipment.

BACKGROUND Field of Disclosure

The present disclosure relates to wireless communications devices andinfrastructure equipment configured to perform a handover of a wirelesscommunications device in a wireless communications network, and methodsof performing a handover.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presenttechnique.

Fourth generation mobile communication networks are able to supportsophisticated services that demand high bandwidth and low latency datatransmission. Efforts are now being targeted at a new technology thatwill further increase the range of services that can be delivered towireless communication devices. It is expected that this new technologywill be based on a new core network architecture. Radio access equipmentthat operates according to a fourth generation radio technology (LTE)may be able to connect to a core network operating according to the newarchitecture.

However, given the wide spread deployment of fourth generation networksand their associated enhanced packet core, EPC, core networks, there isa desire that wireless communications devices are able to obtain servicefrom both types of networks; furthermore it is desirable that seamlessmobility (i.e. handover) is possible between the types of network.

SUMMARY OF THE DISCLOSURE

According to one example embodiment of the present technique, there isprovided a method performed in a first infrastructure equipment for ahandover of a wireless communications device from the firstinfrastructure equipment as a source to a second infrastructureequipment as a target. The method comprises maintaining a mappingbetween a plurality of packet bearers and a data radio bearer for thewireless communications device, each of the plurality of packet bearersbeing configured to provide a specified quality of service, determiningthat the wireless communications device should handover from the firstinfrastructure equipment to the second infrastructure equipment,determining that the second infrastructure equipment does not supportthe mapping of the plurality of packet bearers to the data radio bearer,and providing an indication of a mapping of the plurality of packetbearers for the second infrastructure equipment after handover to one ofa core network equipment and the second infrastructure equipment forconfiguration of at least one of the radio bearer and the plurality ofpacket bearers at the second infrastructure equipment after thehandover. As a result handover can be performed when the secondinfrastructure equipment does not support the mapping of a plurality ofpacket bearers to a data radio bearer. Further respective aspects andfeatures are defined by the appended claims.

The foregoing paragraphs have been provided by way of generalintroduction, and are not intended to limit the scope of the followingclaims. The described embodiments, together with further advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 is a schematic block diagram illustrating an example of a mobiletelecommunication system including eNBs connected to a 5G core networkand/or an enhanced packet core network;

FIGS. 2A and 2B illustrate an example of logical channels which are usedfor transmissions between a core networks, eNBs and UE of FIG. 1;

FIGS. 3A and 3B illustrate example protocols and protocol data unitsused for transmissions over the logical channels illustrated in FIGS. 2Aand 2B respectively;

FIG. 4 is an example message sequence diagram corresponding to aninter-system handover for a UE between an eNB connected to a 5G corenetwork and an eNB connected to a EPC core network;

FIG. 5 is an example message sequence diagram illustrating a techniquefor a handover preparation phase in accordance with an embodiment of thepresent technique;

FIG. 6 is an example message sequence diagram illustrating a furthertechnique for a handover preparation phase in accordance with anembodiment of the present technique;

FIG. 7 is an example message sequence diagram illustrating yet a furthertechnique for a handover preparation phase in accordance with anembodiment of the present technique;

FIG. 8 is an example message sequence diagram illustrating a techniquefor the forwarding of data as part of a handover procedure between eNBsconnected to different core networks;

FIG. 9 is an example message sequence diagram illustrating a furthertechnique for the forwarding of data as part of a handover procedurebetween eNBs connected to different core networks; and

FIG. 10 is an example message sequence diagram illustrating yet afurther technique for the forwarding of data as part of a handoverprocedure between eNBs connected to different core networks.

DETAILED DESCRIPTION OF THE EMBODIMENTS Conventional CommunicationsSystem

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a mobile telecommunications network/system which may beadapted to implement embodiments of the disclosure as described furtherbelow. Various elements of FIG. 1 and their respective modes ofoperation are well-known and defined in the relevant standardsadministered by the 3GPP® body, and also described in many books on thesubject, for example, Holma H. and Toskala A [1]. It will be appreciatedthat operational aspects of the telecommunications network which are notspecifically described below may be implemented in accordance with anyknown techniques, for example according to the relevant standards.

The network includes a plurality of base stations 101, 102, 103connected to two core networks 105 and 106. Each of the base stationsprovides one or more coverage areas (i.e. cells) within which data canbe communicated to and from a communications device 104. Data istransmitted from the base stations 101, 102, 103 to communicationsdevices such as the communications device 104 within their respectivecoverage areas via a radio downlink. Data is transmitted fromcommunications device such as the device 104 to the base stations via aradio interface which provides a radio uplink and a radio downlink. Theuplink and downlink communications may be made using radio resourcesthat are licenced for exclusive use by an operator of the network. Thecore networks 105 and 106 route data to and from the communicationsdevice 104 via the respective base stations and provides functions suchas authentication, mobility management, charging and so on.Communications devices may also be referred to as mobile stations, userequipment (UE), user device, mobile radio, and so forth. Base stationsmay also be referred to as transceiver stations/NodeBs/eNodeBs (eNB forshort), and so forth.

The base stations or eNodeBs and UE described herein may comprise atransmitter (or transmitter circuitry), a receiver (or receivercircuitry), and a controller (or controller circuitry). A controller maybe, for example, a microprocessor, a CPU, or a dedicated chipset, etc.,configured to carry out instructions which are stored on a computerreadable medium, such as a non-volatile memory. The processing stepsdescribed herein may be carried out by, for example, a microprocessor inconjunction with a random access memory, operating according toinstructions stored on a computer readable medium. The base stations oreNodeBs may comprise more than one communications interface (andassociated transmitter and receiver circuitry), such as a wirelesscommunications interface for communication with one or more UEs and acommunications interface (which may be wired or wireless) forcommunication with one or more core network equipment.

Wireless communications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division modulation (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiple access scheme (SC-FDMA) on the radio uplink. Other examples ofwireless communications systems include those operating in accordancewith 5G in which a radio network is formed by infrastructure equipmentreferred to as wireless transceiver units.

In a conventional fourth generation mobile network, service to userequipment such as the user equipment 104 is provided by a combination ofa radio access network comprising one or more eNodeBs, such as theeNodeB 102, connected to an enhanced packet core (EPC) network such asEPC network 106 which may comprise core network equipment (not shown indetail).

The eNodeBs 101 and 103 are examples of base stations according to apossible future network architecture (which may be referred to as ‘5G’)in which the radio access network is connected to a new core networksuch as 5G core network 105 which may comprise core network equipment(not shown in detail). It may be that an eNodeB such as the eNodeB 103is simultaneously connected to two core networks such as the corenetwork 106 and the core network 105.

The 5G core network 105 may comprise one or more Access and MobilityManagement Functions (AMF) (not shown in FIG. 1). The eNodeBs 101 and103 may be connected to an AMF within the 5G core network 105.

The eNodeBs 101, 102 and 103 may operate substantially in accordancewith an LTE specification (or variants and updates thereof) at least inrespect of the radio interface between the eNodeB and the UE 104.

However in light of the use of different core networks there can beexpected to be differences between the operation of interfaces betweenthe core network and the eNodeBs i.e. between the eNodeBs 102 and 103and the EPC core network 106 and between the eNodeB's 103 and 101 andthe 5G core network 105. These differences may support, for example,different types of end to end flows.

An example of these differences is shown in FIGS. 2A and 2B whichillustrate possible logical connections between the respective corenetworks and UE 104. Data received by the core networks 105, 106 fortransmission to the UE 104 is typically formed of packets which areformatted according to a specified protocol. In the followingdescription, it is assumed that these packets are formed in accordancewith an internet protocol (IP). However, it will be appreciated that anyother appropriate packet format may be used instead.

FIG. 2A shows the logical connections between the 5G core network 105,the eNodeB 101 and the UE 104. An IP packet received in the 5G corenetwork 105 is assigned to a particular quality of service (QoS) flowsuch as QoS flows 201, 202 and 203. Each of the QoS flows may becharacterised by a QoS flow ID and may be associated with a quality ofservice requirement (such as one or more of a guaranteed bit rate, amaximum bit rate, a maximum latency, a permitted packet loss ratio andthe like). Although not shown in FIG. 2A, the QoS flows 201, 202 and 203are end to end between the 5G core network 105 and the UE 104. That isto say the UE knows the parameters associated with each of the QoS flows201, 202, 203.

An eNodeB connected to the 5G core network such as the eNodeB 101 isalso aware of the QoS flows. The eNodeB 101 establishes logicalconnections with the UE which may be data radio bearers (DRB) 204 and205. These may operate substantially in accordance with thespecifications for LTE radio bearers. Each of the DRBs 204 and 205 maybe associated with a pair of corresponding packet data convergenceprotocol (PDCP) entities described below.

In accordance with a 5G system architecture as shown in FIG. 2A, one DRB(such as the DRB 204) may be used to transport packet data associatedwith two QoS flows (such as the QoS flows 201 and 202). In order toaccommodate this flexibility, the eNodeB 101 may maintain a mappingtable such as table 206 or equivalent in order to store a mappingbetween each of the QoS flows and the respective DRB. Using the table,the eNodeB 101 is able to assign packets received from the 5G corenetwork 105 over the QoS flows 201, 202, 203 to the appropriate dataradio bearers 204 and 205 for transmission to the UE 104.

The architecture according to conventional LTE and EPC specifications isshown in FIG. 2B. An IP packet received in the enhanced packet corenetwork 106 is associated with an evolved packet system (EPS) bearersuch as an EPS bearer 207. The EPS bearers are transported by means ofan S1 bearer (such as S1 bearer 208) between the EPC and the eNodeB andby means of a radio bearer (such as radio bearer 209) to the UE 104.

Unlike the architecture of FIG. 2A, the EPC architecture as illustratedin FIG. 2B is based on a one-to-one mapping between EPS bearers andradio bearers. The eNodeB (such as the eNodeB 102 of FIG. 2B) maintainsa table (such as table 210) which maps one S1 bearer to one radio bearerand thus provides end-to-end EPS bearer connectivity between the EPCcore network and the UE.

FIGS. 3A and 3B show protocols and corresponding PDU formats used in thearchitectures shown in FIGS. 2A and 2B respectively. It will beappreciated that the embodiments described herein may apply in scenarioswhere additional protocols, which are not shown in FIGS. 3A and 3B, areused; for example, radio interface protocols such as a radio linkcontrol (RLC) protocol, a medium access control (MAC) protocol andphysical layer protocols may be used to provide the radio interfacebetween the eNodeB and the UE. Protocols that operate above the IPprotocol layer, such as a user datagram protocol (UDP), a transmissioncontrol protocol (TCP) and a hypertext transfer protocol (HTTP), mayalso be used. Transport protocols such as those that operate between thecore network and the eNodeB may also be used.

FIG. 3A shows an IP packet 301 which is received from the 5G corenetwork 105 by the eNodeB 101. The IP packet 301 is associated with aprotocol data unit (PDU) session (not shown), and a QoS flow, such asone of the QoS flows 201, 202, 203 of FIG. 2A. The PDU session maycomprise multiple QoS flows and, in the example of FIG. 3A, the QoSflows 201, 202, 203 may all be associated with (that is, form a part of)the same PDU session. In order to provide the mapping between multipleQoS flows and a single radio bearer as described above, a service dataadaptation protocol (SDAP) protocol is used by the eNodeB 101 and UE104. Packets, such as packet 302, transmitted by the eNodeB to the UEinclude a corresponding header generated according to the SDAP protocol.In addition, the packet 302 is generated in accordance with the PDCPprotocol, and includes a header generated by the PDCP protocol. AlthoughFIG. 3A shows only a single SDAP entity and a single PDCP entity at eachof the UE and the eNodeB, there may be multiple SDAP entities and/ormultiple PDCP entities. In particular, there may be one pair of SDAPentities (a pair comprising an entity at the UE and a peer entity at theeNodeB) associated with a PDU session and one pair of PDCP entities foreach radio bearer. For example, referring to FIG. 2A, DRB 204 may havean associated PDCP entity and an associated SDAP entity at the eNodeBand an associated PDCP entity and an associated SDAP entity at the UE.In some instances, SDAP is used only where multiple QoS flows are mappedto a single radio bearer.

In contrast, as shown in FIG. 3B, an IP packet 303 received by theeNodeB from the EPC core network 106 is processed according to a PDCPprotocol and accordingly, a packet 304 transmitted by the eNodeB to theUE includes a PDCP header. Since SDAP is not used for IP packetsreceived from the EPC core network, there is no SDAP header included inthe packet 304. Although FIG. 3B shows only a single PDCP entity at eachof the UE and the eNodeB, there may be multiple PDCP entities—inparticular, there may be one pair of PDCP entities for each radiobearer.

The term ‘protocol entity’ as used herein is used to illustrate thevarious processing steps carried out by an eNodeB or a UE. That is, theexistence of an entity of a protocol implies that processing is carriedout on certain data either to be transmitted or received, in accordancewith the specifications of that protocol. The protocol may, for example,specify the addition or removal of header information, data compressionor decompression, the maintenance of state information based on thetransmission or reception of data or other functions as will be known tothe skilled person. Protocol entities may be logically arranged withinan entity such as the UE 104 or the eNodeBs 101,102 to process the datasequentially according to a defined sequence, for example in accordancewith a layered protocol model such as the well-known OSI protocol model.

Example Embodiments

The problems that are addressed by the embodiments of the presenttechnique relate to the different architectures used and different setof protocols used by the eNodeB's 101, 102 and their respective corenetworks 105, 106. Embodiments of the present technique addresstechnical problems in the handover preparation phase which arise as aresult of the possibility of mapping multiple QoS flows to a single dataradio bearer according to a 5G network architecture, while nocorresponding mapping is possible in the EPC architecture. As shown inFIGS. 3B and FIG. 2B, the mapping between EPS bearer and radio bearer ison a one-to-one basis. Further embodiments of the present techniqueaddress the data forwarding step shown in 403 and 404 of FIG. 4(described below) in light of the architectural differences describedabove.

FIG. 4 illustrates a handover procedure in which embodiments of thepresent technique may be applicable. The UE 104 is initially served by acell controlled by the eNodeB 101 which is connected to the 5G corenetwork 105. As such, the UE 104 has established one or more QoS flows,which it receives over one or more radio bearers from the eNodeB 101.After the handover, the UE 104 is served by a cell controlled by theeNodeB 102 which is connected to the EPC core network 106.

At some point (not shown in FIG. 4), the eNodeB 101 determines that itis appropriate for the UE to be transferred to the control of the eNodeB102. This may be based on handover criteria being met. Thisdetermination may be based on measurement reports received from the UEor on signal strength measurements or signal quality measurements madeby the eNodeB in respect of signals received from the UE or based on acurrent load of the eNodeB 101 or on any other appropriate factors.

In some embodiments, the source eNodeB 101 and the target eNodeB 102 maybe the same eNodeB (e.g. they may be eNodeB 103), having connections toboth the 5G core network 105 and the EPC network 106. In some suchembodiments, the eNodeB may control multiple cells, and the handover maybe between different cells which are controlled by the same eNodeB; inother such embodiments, the handover may be an intra-cell handover; thatis, the source and target cells may be the same.

In response to the determining that the handover criteria are met, ahandover preparation phase 401 is initiated by the eNodeB 101. As partof the handover preparation phase, the eNodeB 101 may determinecapabilities of the target eNodeB 102, such as whether it is connectedto an EPC network or a 5G core network (or both). The eNodeB 101 mayalso determine (for example, based on the determined connectivity ofeNodeB 102) whether the handover must be initiated via the 5G corenetwork, by means of signalling between the eNodeB 101 and the 5G corenetwork 105, or whether the handover may be initiated directly with theeNodeB 102, such as by means of an interface connecting the two eNodeBsdirectly.

The eNodeB 101 transmits a request (either directly, or via the 5G corenetwork 105) to the eNodeB 102 informing the eNodeB 102 that itconsiders handover criteria to have been met in respect of the UE 104,and in respect of a target cell which is under the control of the eNodeB102.

In some embodiments, the source eNodeB does not determine an identity ofthe target eNodeB, but may rely on a routing functionality within the 5Gcore network and/or the EPC network to route messages appropriatelybased on, for example, a globally unique cell identifier associated withthe target cell.

The eNodeB 102 reserves radio resources for the use of the UE 104 in thetarget cell and confirms to the eNodeB 101 that it is able to accept thehandover of UE 104. A description of the reserved radio resources may beincluded in a signalling message sent from the eNodeB 102 to the eNodeB101, for onward transmission to the UE 104. In some embodiments of thepresent technique, the description of the reserved radio resourcesincludes a mapping of radio bearers to EPS bearers. In some embodimentsit may indicate (explicitly or implicitly) that packets that would havebeen associated with the QoS flows that are active in the source cell(such as the flows 201, 202 and 203 of FIG. 2A) will all be carried overa single EPS bearer, such as the EPS bearer 207 in FIG. 2B.Alternatively, a different mapping may be indicated explicitly.

As will be appreciated, the handover preparation phase 401 may includeother steps and other signalling.

Subsequent to the handover preparation phase, handover execution thenoccurs at step 402. In this step the UE 104 is commanded to change itsserving cell and to connect to the target eNodeB 102. As a result, itobtains service (i.e. data connectivity) via the EPC 106 and eNodeB 102in the target cell. At this point in some embodiments, the UE 104 usesone or more of the EPS bearers configured for the use of the UE 104 inthe target cell, and uses an EPS bearer to DRB (one-to-one) mapping, inplace of the QoS flow to DRB mapping that was in use in the source cell.

It is desirable that no packets are lost as a result of this handoverprocedure; that is, that all IP packets destined for the UE, whetherreceived at the 5G core network 105 or at the EPC network 106, areultimately delivered to the UE. It may be the case that IP packets arereceived by the eNodeB 101 from the 5G core network 105 but are nevertransmitted to the UE 104 by eNodeB 101 because, for example, the eNodeB101 does not have an opportunity to transmit these IP packets before theUE changes its serving cell as part of the handover execution phase 402.Alternatively it may be that an IP packet received from the 5G corenetwork by eNodeB 101 was transmitted to the UE 104 but was notsuccessfully received by the UE. The eNodeB 101 may identify thissituation by the lack of receipt of a positive acknowledgement of the IPpacket from the UE 104.

To mitigate these scenarios, packets may be transmitted by the sourceeNodeB 101 to the target eNodeB 102 as shown in step 403 for onwardtransmission in step 404 to the UE 104. In some embodiments, the dataforwarding steps 403 and 404 form a part of the handover execution phase402. For clarity in the following descriptions, they are described asbeing separate from the handover execution phase 402; however, this isnot intended to limit the scope of the techniques described herein toexclude embodiments in which data forwarding (such as data forwardingsteps 403 and 404) is considered part of the handover execution phase(such as the execution phase 402).

Preparation Phase

FIG. 5 illustrates an example embodiment of the present technique, inwhich the UE 104 is connected to the source eNodeB 101 which is aneNodeB controlling an LTE cell and which is connected to the 5G corenetwork 105.

In step 501 the eNodeB which is controlling the UE determines thathandover criteria are met in respect of a target cell controlled byeNodeB 102.

In response to determining that the handover criteria are met, theeNodeB 101 determines that it is appropriate to notify the 5G corenetwork that the handover has been triggered by means of a signallingmessage such as message 502. According to embodiments of the presenttechnique, the eNodeB 101 determines that the target cell is controlledby an eNodeB (such as the eNodeB 104) which is connected to an EPCnetwork such as EPC network 106. Responsive to this determination, thenotification 502 to the 5G core network 105 may include a handover typeindication of “5GC to EPC”. More generally, the notification 502 mayinclude a handover type information element indicative that, althoughthe source and target radio technologies may be both the same (e.g. bothbased on LTE), the core networks by which the connectivity for the UE104 is to be achieved after handover is different from the core networkby which connectivity is to be achieved prior to the handover. Forexample, the notification 502 may indicate that the current core networkis the 5G core network 105, and that the second core network will be theEPC network 106.

In other embodiments not shown in the figures, a notification from aneNodeB which is connected to an EPC network may indicate to the EPCnetwork that the handover corresponds to a type whereby the first(current) core network is an EPC core network, and the second (target)will be an 5G core network.

Notifying the 5G core network that the target cell is EPC connected mayensure that the 5G core network is able to direct further signaling inrespect of the handover preparation phase towards the appropriate EPCcore network and may be used by the 5G core network to perform anynecessary mapping between QoS flows in the 5G core network and EPSbearers in the EPC core network.

According to other example embodiments, the eNodeB 101 also transmits tothe 5G core network equipment a representation of its mapping table 206which indicates the correspondence between data radio bearers, such asDRBs 204 and 205, by which the source eNodeB 101 communicates with theUE 104, and end-to-end QoS flows, such as QoS flows 201, 202, 203, bywhich IP packets are transferred from the 5G core network 105 to the UE104. This is indicated in step 503. Steps 503 and 502 may comprise thetransmission of two separate messages or may be combined in a singlemessage.

In addition, the source eNodeB 101 may include in a message containingindications 502 and/or 503 a transparent container which is aninformation element constructed by the eNodeB 101 to be passed to thetarget eNodeB 102 having been transmitted transparently via the corenetworks 105, 106.

A benefit of this example embodiment is that a source eNodeB (such aseNodeB 101) does not need to be aware of a QoS flow to EPS bearermapping that will be used when the handover is carried out. In such anembodiment the necessary mapping between the QoS flows and EPS bearer isperformed after the handover by the 5G core network.

FIG. 6 shows an alternative embodiment of the present technique. In step601, the eNodeB 101 receives from the 5G core network 105 an indicationof a mapping that will be used between EPS bearers and QoS flows shoulda handover occur. This may occur as part of an establishment procedurefor the QoS flows. The process then proceeds with step 501 and step 502as already described above.

The eNodeB 101 constructs an EPS configuration indication 603 bycombining the EPS bearer to QoS flow mapping received in step 601 withthe QoS flow to DRB mapping table 206. In some embodiments, theresulting indication comprises an EPS bearer to DRB mapping. In someembodiments this may result in an EPS configuration indication 603 whichcan be understood by the target eNodeB 102 even if the eNodeB 102 is nota 5G-aware eNodeB—that is to say, has not been upgraded to supportfunctionality associated with interworking with 5G core networks. Insome embodiments, the EPS configuration indication 603 comprises a QoSflow to EPS bearer mapping associated with a DRB configuration that isin use by the source eNodeB 101

In step 602, the eNodeB 101 transmits to the 5G core network 105 atransparent container for onward transmission to the target eNodeB 102containing the EPS configuration indication 603.

eNodeB 102 may receive the transparent container in message 604, whichmay be a Handover Request message.

A benefit of this embodiment is that it may be used in the case of an X2based handover in which the transparent container containing the EPSconfiguration indication 603 may be sent directly from source eNodeB 101to target eNodeB 102 without passing through the core networks 105, 106.

FIG. 7 shows an alternative embodiment of the present technique. In theembodiment of FIG. 7, the process starts as in FIG. 5 with steps 501 and502. In step 704, the eNodeB 101 sends a message to the 5G core networkincluding a transparent container which includes a data radio bearer(DRB) to QoS mapping indication 701. This may be a representation oftable 206. The target eNodeB 102 may receive the transparent containerin a message 705, which may be a Handover Request message. Based on theindication 701, eNodeB 102 maps QoS flows used in the 5G core network105 (such as the QoS flows 201, 202, 203) to EPS bearers (such as theEPS bearer 207) used in the EPC network 106, and hence determines anappropriate data radio bearers for each of the IP packets which areassociated with the respective QoS flows.

In some embodiments, 5G core network 105 provides a QoS flow to EPSbearer mapping (which may be substantially the same as the informationdescribed above in step 601 of FIG. 6) to the EPC network 106. In someembodiments, the EPC network 106 provides the QoS flow to EPS bearermapping to the target eNodeB 102, and the target eNodeB 102 performs themapping of the QoS flows and radio bearers indicated in indication 701to the corresponding EPS bearers based on the QoS flow to EPS bearermapping received from EPC core network 106.

In some embodiments, the target eNodeB 102 determines that a fullconfiguration handover is required. This determination may be based onthe determination that the target eNodeB 102 is unable to parse thetransparent container received from the eNodeB 101. For example (asshown in step 702) it may determine that that critical information whichit expects to receive in a transparent container (e.g. in accordancewith a specification) is missing. In one example, it may determine afull configuration handover is to be performed based on an absence of anidentifier of an EPS bearer in a transparent container (such as thetransparent container containing indication 701) received from thesource eNodeB 101. In a further example, the target eNodeB 102determines that a full configuration is required if a security algorithmin use in the source cell is not supported in the target cell (e.g.because it is not supported by the EPC core network 106).

The determination to perform a full configuration handover may be basedon predetermined conditions comprising one or more of the above.

In some embodiments a determination to perform a full configurationhandover by the eNodeB 102 precludes a determination that the handoveris considered to have failed, as may be done in a conventional approach.

Responsive to this determination, initiates a full configurationhandover in which resources in a target cell are reserved and associatedwith an EPS bearer, without reference to, for example, data radiobearers used for corresponding EPS bearers or QoS flows in a previouscell. According to some embodiments in which a full configurationhandover is performed, after the handover execution phase the UE 104discards, or operates without reference to, any PDCP protocol stateinformation stored while operating in the source cell, regardless ofwhether a radio bearer corresponding to the respective PDCP protocolentity is operating in an acknowledged mode or in an unacknowledgedmode.

According to some embodiments in which a full configuration handover isperformed, the target eNodeB 102 constructs a handover command messagewhich is transmitted in a transparent container, such as the transparentcontainer 708 indicated by a dashed line in FIG. 7, to the UE 104 whichincludes a description of the radio resources reserved in the targetcell without reference to the configuration of the radio resources whichare assigned to the UE 104 by the source eNodeB 101 for use by the UE104 in the source cell. In some embodiments in which a fullconfiguration handover is performed, the description of the radioresources includes an indication of the correspondence between reservedradio resources and one or more EPS bearers.

The transparent container 708 containing the handover command istransported from the target eNodeB 102 to the UE 104 by means ofmessages 703, 706, 707 sent via the core networks 105, 106 and thesource eNodeB 101. (Messages carrying the transparent container withinor between the core networks 105, 106 are not shown).

After receiving the transparent container 708, in some embodiments theUE 104 may determine that an identity of a core network bearer (such asan identity of the QoS flows 201, 202, 203) which is active in thesource cell is not present in the handover command. Responsive to thisdetermination, the UE 104 nevertheless proceeds with the handover. Inparticular, the UE 104 does not determine that the handover message iserroneous. In some embodiments, the UE 104 further determines that thehandover message is not erroneous, based on a presence of the identityof a bearer (such as the identity of the EPS bearer 207) of the typecorresponding to the core network technology (e.g. 5G, EPC) associatedwith the target cell.

According to some embodiments in which a full configuration handover isperformed, the handover command message describes radio resources whichare associated with one or more EPS bearers for use in the target cell.However, the UE 104, when operating in the source cell and connected tothe source eNodeB 101, associated IP packets with one or more QoS flows.Therefore, in some embodiments, the UE 104, based on a combination of aQoS flow to EPS bearer mapping and the previous QoS flow description,determines which EPS bearer (and therefore which radio bearer andcorresponding radio resources) in the target cell to associate with anIP packet which is to be transmitted in the target cell to the targeteNodeB 102. The UE 104 transmits the IP packet to the target eNodeB 102in accordance with this determination. In some embodiments, the UEreceives a representation of the QoS flow to EPS bearer mapping eitherprior to or during a handover preparation phase (such as the handoverpreparation phase 401).

The embodiment shown in FIG. 7 has the benefit that it does not requirethe eNodeB 101 to have received the EPS bearer to QoS flow mapping andit further simplifies the operation of the eNodeB 101 because theindication 701 sent in the transparent container is information that ithas readily available without requiring any further mapping.

In the embodiments described above, one or more of the indicationstransmitted from the source eNodeB to the 5G core network (such asmessages 502, 503, 602, 704) may be transmitted in a Handover Requiredmessage.

The transparent containers 603, 701 may be forwarded from the sourceeNodeB 101 to the target eNodeB 104 via the 5G core network 105 and theEPC network 106. The transparent container may contain an RRC Handoverpreparation information element, which may be in conformance with an RRCHandoverPreparationInformation information element defined in 3GPP TS36.331.

The transparent containers 603, 701 may be transmitted directly from thesource eNodeB 101 to the target eNodeB 104 via an interface (such as anX2 interface) between the eNodeBs which does not require the transparentcontainer to traverse a core network. The transparent container in thiscase may be sent in a Handover Request message.

Data Forwarding

FIG. 8 is a message flow diagram illustrating aspects of an embodimentof the technique which addresses the problem of forwarding data from thesource eNodeB 101 to the target eNodeB 102 to ensure reliable deliveryof all IP data packets.

The process starts with IP packets such as IP packet 301 beingtransmitted from the 5G core network to the eNodeB 101, where they areassociated—as illustrated in FIG. 2A—with a QoS flow such as QoS flow201. These messages are then processed according to the SDAP protocoland PDCP protocol in the eNodeB 101 as illustrated in FIG. 3A and aretransmitted to UE 104 as data packets such as the data packet 302 whichincludes the IP packet together with an SDAP header and a PDCP header.

The details of the handover preparation phase and the handover executionphase have broadly been described above and are omitted here forconciseness.

Once the handover execution phase is complete, the UE 104 is no longerserved by the source eNodeB 101 and any IP packets which remain storedat the eNodeB 101, which have not been positively acknowledged as havingbeen received by UE 104, must be forwarded to eNodeB 102. As describedabove, in accordance with embodiments described herein, the forwardingof IP packets may be carried out after the handover execution phase (asillustrated in FIGS. 8, 9, and 10) or as part of the handover executionphase.

In the embodiment illustrated in FIG. 8, the eNodeB 101 may have alreadyassociated a PDCP sequence number with an IP packet received from the 5Gcore network 105. The eNodeB 101 may, in addition, have alreadyconstructed a data packet for transmission to the UE 104 which includesboth an SDAP header and a PDCP header. In the embodiment of FIG. 8, thePDCP header and the SDAP header are removed, if they have been alreadyconstructed, and the IP packet is forwarded together with the PDCPsequence number in message 803 from the source eNodeB 101 to the targeteNodeB 102.

The message 803 may be transmitted directly from the eNodeB 101 to theeNodeB 102, for example, by means of an X2 interface, or it may betransmitted indirectly via the respective core networks 105, 106. TheeNodeB 102 processes the forwarded IP packet according to the PDCPprotocol, based on the PDCP sequence number received from the sourceeNodeB 101. It then forwards the IP packet complete with a PDCP headerto the UE in message 804.

As will be appreciated, this corresponds to the format used fortransmission of IP packet 304 in FIG. 3B; that is to say, the format ofthe data transmitted from eNodeB 102 to the UE complies with the formatthat would be expected for packets received directly from the EPCnetwork, such as IP packet 805 which is transmitted to the UE intransmission 806.

The embodiment shown in FIG. 8 therefore has the advantage that noadditional functionality is required in target eNodeB 102 above andbeyond that which is already required in respect of handovers from otherEPC-connected eNodeBs.

In some embodiments, the UE 104 releases its SDAP entity at the point atwhich handover execution occurs; in other words, at the point at whichit expects to no longer receive packets which have been processed by theSDAP entity of the source eNodeB 101. In some further embodiments, theinclusion of the PDCP sequence number in message 803 is optional. Infurther embodiments the PDCP sequence number is omitted for alltransmissions 803.

In some embodiments, the source eNodeB 101 determines whether a fullconfiguration handover has been performed. In some embodiments thesource eNodeB 101 may determine whether the number of PDCP entitiesassociated with the UE 104 will be the same in the target eNodeB 102after the handover execution as it is in the source eNodeB 101.

If the source eNodeB 101 determines that full configuration handover hasbeen performed, or if the source eNodeB 101 determines that the numberof PDCP entities associated with the UE 104 will not be the same in thetarget eNodeB 102 as it is in the source eNodeB 101, the source eNodeBforwards IP packets to the target eNodeB, with no associated PDCPsequence number and without any SDAP or PDCP headers.

In some embodiments, the source eNodeB 101 determines on apacket-by-packet basis whether or not a PDCP sequence number has beenassigned to a particular packet such as the packet 301. If no sequencenumber has been assigned, the source eNodeB forwards the IP packet tothe target eNodeB 102, with no associated PDCP sequence number or SDAPor PDCP headers.

In some embodiments, if the source eNodeB determines that a fullconfiguration handover has not been performed, and that the number ofPDCP entities associated with the UE 104 will be the same in the targeteNodeB 102 as it is in the source eNodeB 101, and that a PDCP sequencenumber has been assigned to a particular packet, then the packet isforwarded, together with the PDCP sequence number and, in someembodiments, together with an SDAP header.

FIG. 9 illustrates a further embodiment of the present technique. InFIG. 9, the messages 301 and 302 are as already described above. In theembodiment shown in FIG. 9, once the eNodeB 101 identifies that it has apacket to be forwarded to the target eNodeB 102 the packet is forwardedas shown at step 901, formatted to include the IP packet and an SDAPheader and sent together with a PDCP sequence number. No PDCP header isincluded in the transmission 901. In this embodiment, a representationof the mapping between the QoS flows and the EPS bearers is received bythe target eNodeB 102 (not shown in FIG. 9), and this information isused to map each packet received from source eNodeB 101 to anappropriate radio bearer (such as the radio bearer 209) that has beenestablished between the target eNodeB 102 and the UE 104. Based on themapping, and taking into account the SDAP header associated with thetransmission 901, the target eNodeB 102 associates the IP packet and thePDCP sequence number with an appropriate PDCP entity which is currentlyin operation and which has a peer corresponding entity at the UE 104.

The eNodeB 102 removes the SDAP header from the packet received intransmission 901 and attaches an appropriate PDCP header in atransmission 902 to the UE 104.

In the example shown in FIG. 9 the processing, whereby the QoS flow toEPS bearer mapping is made use of to process forwarded packets (such asthe packet in 901), is shown as being co-located with the target eNodeB102. However, this functionality may exist elsewhere in the network as aseparate entity.

As with the embodiment illustrated in FIG. 8, this approach has thebenefit that a packet received by the UE 104 once it is in the targetcell conforms to the protocols used in an EPC-connected cell asillustrated in FIG. 3B. This approach also has the advantage thatpackets which are created in eNodeB 101 for transmission to the UE canbe forwarded with minimal further processing to eNodeB 102 therebysimplifying the implementation of eNodeB 101.

FIG. 10 illustrates yet a further embodiment of the present technique.In FIG. 10, an IP packet such as IP packet 301 is forwarded to UE in amessage 302 which includes an SDAP header and a PDCP header. Afterhandover execution, the eNodeB 101, determining that it has a packetwhich may not have been correctly received by the UE either because itwas never transmitted to the UE or because it was transmitted to the UEbut not acknowledged, forwards the packet to eNodeB 102.

In the embodiment illustrated in FIG. 10, the packet is formatted so asto be understood by the target eNodeB 102 as comprising a PDCP servicedata unit (SDU) together with a PDCP sequence number. As such, themessage 1001 as received by the eNodeB 102 appears to the eNodeB 102 asa message compliant with conventional data forwarding messages usedbetween LTE eNodeBs.

However, in this case the PDCP SDU portion includes, as well an IPpacket, an SDAP header which has been added by an SDAP protocol entityof the source eNodeB 101. The forwarded packet does not include a PDCPheader.

The eNodeB 102 processes the received message 1001 as if it were aforwarded LTE message comprising a PDCP SDU and an associated sequencenumber and constructs a PDCP header based on the PDCP sequence number.The PDCP header is attached to the PDCP SDU and forwarded to the UE 104in step 1002.

Not shown in FIG. 10, the UE 104 receiving the message 1002 processesthe received message according to the PDCP protocol and determines thatthe PDCP SDU contained in the message 1002 includes an SDAP header whichwas generated by the source eNodeB 101. Having determined that the PDCPSDU includes an SDAP header, the UE 104 processes the message inaccordance with the SDAP protocol. In the embodiment illustrated in FIG.10, the UE 104 therefore maintains its SDAP entity (which wasestablished in the source cell prior to handover) after the UE 104 haschanged its serving cell.

In some embodiments, the UE 104 removes its SDAP entity based on adetermination that no further packets are likely to be received whichinclude an SDAP header. This determination may be based on signalling,such as radio resource control (RRC) signalling, received from targeteNodeB 102. Alternatively, the determination may be made responsive tothe expiry of a timer which is started during the handover executionstep. The duration of the timer may be according to a specification, ormay be configured by the network, for example in an RRC reconfigurationmessage transmitted by either the source eNodeB 101 or the target eNodeB102.

The eNodeB 102 may receive a packet directly from the EPC such as the IPpacket 1003. This is processed in the conventional manner by generatinga PDCP header in accordance with the PDCP protocol, and is forwarded asshown in step 1004 to the UE 104, compliant with the format illustratedin 304 of FIG. 3B.

As an alternative to the sequence shown in FIG. 10, the eNodeB A 101 mayhave an IP packet for which no PDCP sequence number has yet beendetermined. In some embodiments, this may be forwarded directly to thetarget eNodeB 102 without a PDCP sequence number and without an SDAPheader. The target eNodeB 102 assigns a PDCP sequence number andconstructs the PDCP header and forwards the resulting message to UE 104.

This approach, as illustrated in FIG. 10, has the benefit that thetarget eNodeB 102 does not need to be upgraded to be able to processforwarded messages which include an SDAP header. Even though suchmessages are received by the target eNodeB 102 (such as message 1001),the target eNodeB 102 processes these in accordance with conventionalprocedures for the receipt of forwarded packets which comprise a PDCPSDU and are associated with a PDCP sequence number.

In some embodiments the UE 104 may, on receipt of a message transmittedfrom the target eNodeB 102 following a handover, make a determination asto whether or not the received message includes an SDAP header and,responsive to that determination, process the received messageaccordingly. In the case where it determines that the SDAP header isincluded, it removes the SDAP header before passing the IP packet tohigher protocol layers. In the case where the message is determined notto include an SDAP header, the UE 104 processes that in accordance theconventional approach for packets received from the target eNodeB 102which have been transmitted to the eNodeB 102 by the EPC core network106 such as packets 1003 and 1004.

In another example embodiment, the source eNodeB 101 determines that apacket has not been successfully transmitted to the UE 104 anddetermines a corresponding sequence number according to a transportprotocol used between the eNodeB 101 and 5G core network. The transportprotocol may be a General Packet Radio Service (GPRS) TunnellingProtocol (GTP) protocol and the sequence number may be a GTP sequencenumber. The source eNodeB 101 then indicates to the 5G core network 105one of i) the sequence number(s) of packet(s) which have not beentransmitted to the UE and ii) the sequence number of the last GTP packet(that is, the GTP packet with the highest sequence number) that has beentransmitted to the UE 104. This indication may be communicated to the 5Gcore network 105 by means of a signalling message (which may be a GTPcontrol protocol data unit or an S1 message sent on an S1 control plane)or by means of a last transmitted sequence number header field in a GTPpacket which is transmitted from the source eNodeB 101 to the 5G corenetwork 105.

Based on this message, the 5G core network 105 forwards the relevantpackets to the EPC for onward forwarding to the target eNodeB 102 andthe UE 104 in the target cell.

In addition, in some embodiments a control plane entity in one of thecore networks 105, 106 (which may be a mobility management entity, MME,or an AMF) transmits an indication of the sequence number(s) of GTPpackets for which data forwarding is required to a serving gateway(S-GW) or entity performing similar functionality.

As will be appreciated by the skilled person, various combinations ofthe embodiments described above are possible. For example, withreference to FIG. 4, embodiments described above which relate to thehandover preparation phase 401 may be combined with embodimentsdescribed above which relate to data forwarding steps 403 and 404 andthe corresponding processing of data.

Various aspects and features of the present technique are defined in theappended claims. Various modifications may be made to the exampleembodiments as disclosed above as appreciated by the skilled personwithin the scope of the appended claims. Various further exampleembodiments and features are defined in the following numberedparagraphs:

Paragraph 1. A method performed in a first infrastructure equipment fora handover of a wireless communications device from the firstinfrastructure equipment as a source to a second infrastructureequipment as a target, the method comprising

-   -   maintaining a mapping between a plurality of packet bearers and        a data radio bearer for the wireless communications device, each        of the plurality of packet bearers being configured to provide a        specified quality of service,    -   determining that the wireless communications device should        handover from the first infrastructure equipment to the second        infrastructure equipment,    -   determining that the second infrastructure equipment does not        support the mapping of the plurality of packet bearers to the        data radio bearer, and    -   providing an indication of a mapping of the plurality of packet        bearers for the second infrastructure equipment after handover        to one of a core network equipment and the second infrastructure        equipment for configuration of at least one of the radio bearer        and the plurality of packet bearers at the second infrastructure        equipment after the handover.

Paragraph 2. A method according to paragraph 1, wherein the providing anindication of a mapping of the plurality of packet bearers for thesecond infrastructure equipment after handover includes

-   -   providing an indication of the mapping between the plurality of        packet bearers and the data radio bearer for the wireless        communications device maintained by the first infrastructure        device.

Paragraph 3. A method according to paragraph 1, the method comprising:

-   -   receiving from the core network equipment an indication of a        mapping of the plurality of packet bearers to one or more packet        bearers for the second infrastructure equipment after handover,        and    -   wherein the providing an indication of a mapping of the        plurality of packet bearers for the second infrastructure        equipment after handover includes    -   providing an indication of the mapping from the plurality of        packet bearers to the one or more packet bearers for the second        infrastructure equipment after handover.

Paragraph 4. A method according to any of paragraphs 1 to 3, wherein theproviding the indication of the required mapping of the plurality ofpacket bearers to a corresponding plurality of data radio bearers forthe second infrastructure equipment after handover includes

-   -   generating a signalling message for transmission to the core        network equipment to which the first infrastructure equipment is        connected, the signalling message indicating that the second        infrastructure equipment does not support the mapping of the        plurality of packet bearers to the data radio bearer, and    -   sending the signalling message to the core network equipment in        preparation for the handover.

Paragraph 5. A method according to paragraph 4 wherein the signallingmessage provides an indication of the mapping of a plurality of radiobearers to the plurality of packet bearers for configuring the secondinfrastructure equipment via an interface between the secondinfrastructure equipment and a second core network to which the secondinfrastructure equipment is connected.

Paragraph 6. A method according to paragraphs 1 or 2, wherein theproviding the indication of the mapping of the plurality of packetbearers for the second infrastructure equipment after handover includes

-   -   generating a transparent container for transmission to the        second infrastructure equipment, the transparent container        including a representation of the mapping, and    -   transmitting the transparent container to the second        infrastructure equipment.

Paragraph 7. A method according to paragraph 4, wherein the transparentcontainer is transmitted to the second infrastructure equipment from thefirst infrastructure equipment via an interface between the firstinfrastructure equipment and the second infrastructure equipment.

Paragraph 8. A method performed in a first infrastructure equipment notsupporting a mapping of a plurality of packet bearers to a data radiobearer for a handover of a wireless communications device from a secondinfrastructure equipment as a source to the first infrastructureequipment as a target, the method comprising

-   -   receiving a request for the handover of the wireless        communication device,    -   receiving an indication of a mapping of a plurality of packet        bearers for configuration of at least one of a radio bearer and        a plurality of packet bearers after the handover,    -   configuring a radio bearer for the wireless communications        device based on the indication of the mapping of the plurality        of packet bearers,    -   generating a message indicating the configuration of the        reserved radio bearer for transmission to the wireless        communication device.

Paragraph 9. A method of paragraph 8, wherein the message indicating theconfiguration of the reserved radio bearer for transmission to thewireless communication device includes a mapping between the radiobearer and a packet bearer.

Paragraph 10. A method of paragraph 8 or paragraph 9, wherein themessage indicating the configuration of the reserved radio bearer fortransmission to the wireless communication device includes a mappingbetween the radio bearer and at least one of the plurality of packetbearers.

Paragraph 11. A method of paragraph 9, wherein the mapping between theradio bearer and at least one of the plurality of packet bearers is amapping of all of the plurality of packet bearers to the radio bearer.

Paragraph 12. A method of any of paragraphs 8 to 11 wherein theindication of a mapping of a plurality of packet bearers forconfiguration of at least one of a radio bearer and a plurality ofpacket bearers after the handover is received in a transparent containergenerated by the second infrastructure equipment.

Paragraph 13. A method of paragraph 12, comprising

-   -   determining that the transparent container does not comply with        one or more predetermined requirements, and    -   responsive to the determination, configuring the radio bearer        without regards to a configuration of a radio bearer by the        second infrastructure equipment.

Paragraph 14. An infrastructure equipment forming a radio network partof a wireless communications network, configured to transmit data toand/or receive data from a wireless communications device, and totransmit the data to or receive the data from a core network part of thewireless communications network, the infrastructure equipment comprising

-   -   receiver circuitry configured to receive radio signals        transmitted by the wireless communications device via a wireless        access interface,    -   transmitter circuitry configured to transmit radio signals to        the wireless communications device via the wireless access        interface, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry to transmit data to or        receive data from the wireless communications device and to        transmit the data to or receive the data from the core network        via an interface with the core network, wherein the controller        circuitry is configured to    -   to maintain a mapping between a plurality of packet bearers and        a data radio bearer for the wireless communications device, each        of the plurality of packet bearers being configured to provide a        specified quality of service,    -   to determine that the wireless communications device should        handover from the first infrastructure equipment to a second        infrastructure equipment,    -   to determine that the second infrastructure equipment does not        support the mapping of the plurality of packet bearers to the        data radio bearer, and the controller is configured in        combination with the transmitter circuitry    -   to transmit an indication of a mapping of the plurality of        packet bearers for the second infrastructure equipment after        handover to the core network equipment for configuration of at        least one of the radio bearer and the plurality of packet        bearers at the second infrastructure equipment after the        handover.

Paragraph 15. An infrastructure equipment forming a radio network partof a wireless communications network, configured to transmit data toand/or receive data from a wireless communications device, and totransmit the data to or receive the data from a core network part of thewireless communications network, the infrastructure equipment comprising

-   -   receiver circuitry configured to receive radio signals        transmitted by the wireless communications device via a wireless        access interface,    -   transmitter circuitry configured to transmit radio signals to        the wireless communications device via the wireless access        interface, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry to transmit data to or        receive data from the wireless communications device and to        transmit the data to or receive the data from the core network        via an interface with the core network, wherein the controller        circuitry is configured    -   to receive a request for a handover of the wireless        communication device,    -   to receive an indication of a mapping of a plurality of packet        bearers for configuration of at least one of a radio bearer and        a plurality of packet bearers after the handover,    -   to configure a radio bearer for the wireless communications        device based on the indication of the mapping of the plurality        of packet bearers and    -   to generate a message indicating the configuration of the        reserved radio bearer for transmission to the wireless        communication device,    -   wherein the infrastructure equipment does not support a mapping        of a plurality of packet bearers to a data radio bearer.

Paragraph 16. A method for forwarding data received by a firstinfrastructure equipment acting as a source to a second infrastructureequipment acting as a target for a wireless communications device duringhandover, the method comprising:

-   -   receiving first data for transmission to the wireless        communications device from a core network to which the first        infrastructure equipment is connected,    -   generating a first protocol data unit according to a first        protocol, the protocol data unit including the received first        data and a first protocol header,    -   determining that the wireless communications device has        performed the handover,    -   in response to determining that the wireless device has        performed the handover, transmitting the received first data to        a second infrastructure equipment for transmission to the        wireless communications device    -   wherein the first protocol provides a mapping of a plurality of        packet bearers, configured to provide a specified quality of        service, to a data radio bearer.

Paragraph 17. A method according to paragraph 16, further comprising

-   -   determining a sequence number in accordance with a second        protocol,    -   generating a second protocol data unit in accordance with the        second protocol, the second protocol data unit including the        first protocol data unit and the sequence number,    -   transmitting the second protocol data unit to the wireless        communications device.

Paragraph 18. A method according to paragraph 16, comprising

-   -   determining a sequence number in accordance with a second        protocol,    -   transmitting the sequence number to the second infrastructure        equipment.

Paragraph 19. A method according to paragraph 16, comprising

-   -   determining a sequence number in accordance with a second        protocol,    -   wherein transmitting the received data to a second        infrastructure equipment for transmission to the wireless device        comprises transmitting the first protocol data unit together        with the sequence number to the second infrastructure equipment.

Paragraph 20. A method according to any of paragraphs 16 to 19,comprising

-   -   receiving second data for transmission to a wireless        communications device from a core network,    -   generating a third protocol data unit according to the first        protocol, the third protocol data unit including the received        second data and a header in accordance with the first protocol,    -   generating a fourth protocol data unit in accordance with the        second protocol, the fourth protocol data unit including the        third protocol data unit and a sequence number in accordance        with the second protocol,    -   before determining that the wireless communications device has        performed a handover, transmitting the second protocol data unit        to the wireless communications device.

Paragraph 21. An infrastructure equipment forming a radio network partof a wireless communications network, configured to transmit data toand/or receive data from a wireless communications device, and totransmit the data to or receive the data from a core network part of thewireless communications network, the infrastructure equipment comprising

-   -   receiver circuitry configured to receive radio signals        transmitted by the wireless communications device via a wireless        access interface,    -   transmitter circuitry configured to transmit radio signals to        the wireless communications device via the wireless access        interface, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry to transmit data to or        receive data from the wireless communications device and to        transmit the data to or receive the data from the core network        via an interface with the core network, wherein the controller        circuitry is configured    -   to receive first data for transmission to the wireless        communications device from the core network equipment,    -   to generate a first protocol data unit according to a first        protocol, the protocol data unit including the received first        data and a first protocol header,    -   to determine that the wireless communications device has        performed the handover, and in response to determining that the        wireless device has performed the handover, to transmit the        received first data to a second infrastructure equipment for        transmission to the wireless communications device,    -   and the first protocol provides a mapping of a plurality of        packet bearers, configured to provide a specified quality of        service, to a data radio bearer.

Paragraph 22. A method for transmitting data to a wireless device by asecond infrastructure equipment acting as a target after handover from afirst infrastructure equipment acting as a source, the method comprising

-   -   receiving data for transmission to the wireless communications        device, the data including a first portion comprising a header        according to a first protocol, a second portion comprising a        header according to a second protocol, and a third portion,    -   receiving a sequence number associated with the data according        to the second protocol,    -   transmitting the third portion to the wireless communications        device,        wherein the data is received from the first infrastructure        device.

Paragraph 23 An infrastructure equipment forming a radio network part ofa wireless communications network, configured to transmit data to and/orreceive data from a wireless communications device, and to transmit thedata to or receive the data from a core network part of the wirelesscommunications network, the infrastructure equipment comprising

-   -   receiver circuitry configured to receive radio signals        transmitted by the wireless communications device via a wireless        access interface,    -   transmitter circuitry configured to transmit radio signals to        the wireless communications device via the wireless access        interface, and    -   controller circuitry configured to control the transmitter        circuitry and the receiver circuitry to transmit data to or        receive data from the wireless communications device and to        transmit the data to or receive the data from the core network        via an interface with the core network, wherein the controller        circuitry is configured    -   to receive data for transmission to the wireless communications        device, the data including a first portion comprising a header        according to a first protocol, a second portion comprising a        header according to a second protocol, and a third portion,    -   to receive a sequence number associated with the data according        to the second protocol, and the controller is configured to        transmit the third portion to the wireless communications        device, and the data is received from source infrastructure        equipment of the radio network part of the wireless        communications network.

Paragraph 24. A method of receiving data by a wireless communicationsdevice in a wireless network during handover from a first infrastructureequipment acting as a source to a second infrastructure equipment actingas a target, the method comprising:

-   -   receiving by the wireless communications device first data in a        first network cell from a first infrastructure equipment, the        first data comprising a first data portion received by the first        infrastructure equipment from a first core network and a first        protocol header in accordance with a first protocol and a second        protocol header in accordance with a second protocol, the second        protocol header including a sequence number, the first and        second protocol headers being generated by the first        infrastructure equipment,    -   performing a handover to a second cell associated with a second        infrastructure equipment, the second infrastructure equipment        connected to a second core network different from the first core        network,    -   receiving a second data in the second network cell, the second        data comprising a second data portion,    -   determining whether the second data includes a third protocol        header in accordance with the first protocol;    -   if the second data includes the third protocol header in        accordance with the first protocol, removing the third protocol        header before processing the second data in accordance with the        second protocol;    -   receiving third data in the second network cell, the third data        comprising a third data portion received by the second        infrastructure equipment from the second core network and a        header in accordance with the second protocol, the second        protocol header including a sequence number generated by the        second infrastructure equipment.

25. A method according to paragraph 24, wherein the secondinfrastructure equipment is an eNodeB connected to an enhanced packetcore, EPC, network and the receiving the second data includes receivingthe second data from the second infrastructure equipment, which has beenreceived from a 5G core network.

Paragraph 26. A method according to paragraph 24 or 25, wherein thesecond protocol is associated with a radio bearer and provides one ormore of header compression, security, and retransmission of the seconddata.

Paragraph 27. A method according to paragraph 26, wherein the secondprotocol is a packet data convergence protocol (PDCP).

Paragraph 28. A method according to paragraph 24, wherein the receivingthe second data includes receiving the second data from the secondinfrastructure equipment, which has been received by the secondinfrastructure equipment via an interface between the firstinfrastructure equipment and the second infrastructure equipment.

Paragraph 29. A method according to paragraph 24, wherein the receivingby the wireless communications device the first data in the firstnetwork cell from a first infrastructure equipment includes receivingthe first data from the first core network using an internet protocol,IP, packet.

Paragraph 30. A method according to any of paragraphs 24 to 29, whereinthe first protocol provides a mapping of a plurality of packet bearers,configured to provide a specified quality of service, to a data radiobearer.

Paragraph 31. A communications device configured to transmit radiosignals to and/or receive radio signals from a first infrastructureequipment and a second infrastructure equipment of a wirelesscommunications network, the communications device comprising

-   -   a receiver circuit configured to receive radio signals        transmitted by the first and second infrastructure equipment via        a wireless access interface,    -   a transmitter circuit configured to transmit radio signals to        the first and second infrastructure equipment via the wireless        access interface, and    -   a controller circuit configured to control the transmitter        circuit and the receiver circuit to transmit data to or receive        data from the wireless communications network via the first and        second infrastructure equipment, wherein the controller circuit        is configured to control the receiver circuit    -   to receive first data in a first network cell from the first        infrastructure equipment, the first data comprising a first data        portion received by the first infrastructure equipment from a        first core network and a first protocol header in accordance        with a first protocol and a second protocol header in accordance        with a second protocol, the second protocol header including a        sequence number, the first and second protocol headers being        generated by the first infrastructure equipment,    -   to perform a handover to a second cell associated with the        second infrastructure equipment, the second infrastructure        equipment connected to a second core network different from the        first core network,    -   to receive a second data in the second network cell, the second        data comprising a second data portion, the controller configured    -   to determine whether the second data includes a third protocol        header in accordance with the first protocol, and,    -   if the second data includes the third protocol header in        accordance with the first protocol, to remove the third protocol        header before processing the second data in accordance with the        second protocol; and the controller circuit is configured to        control the receiver circuit    -   to receive third data in the second network cell, the third data        comprising a third data portion received by the second        infrastructure equipment from the second core network and a        header in accordance with the second protocol, the second        protocol header including a sequence number generated by the        second infrastructure equipment.

Paragraph 32. A communications device according to paragraph 31, whereinthe second infrastructure equipment is an eNodeB connected to anenhanced packet core, EPC, network and the second data has been receivedby the second infrastructure equipment from a 5G core network.

Paragraph 33. A communications device according to paragraph 31 or 32,wherein the second protocol is associated with a radio bearer andprovides one or more of header compression, security, and retransmissionof the second data.

Paragraph 34. A communications device according to paragraph 33, whereinthe second protocol is a packet data convergence protocol (PDCP).

Paragraph 35. A communications device according to paragraph 31, whereinthe second data has been received by the second infrastructure equipmentvia an interface between the first infrastructure equipment and thesecond infrastructure equipment.

Paragraph 36. A communications device according to paragraph 31, whereinthe first data comprises an internet protocol, IP, packet.

Paragraph 37. A communications device according to any of paragraphs 31to 36, wherein the first protocol provides a mapping of a plurality ofpacket bearers, configured to provide a specified quality of service, toa data radio bearer.

REFERENCES

-   [1] LTE for UMTS: OFDMA and SC-FDMA Based Radio Access, Harris Holma    and Antti Toskala, Wiley 2009, ISBN 978-0-470-99401-6.-   [2] 3GPP TS 36.331-   [3] 3GPP TS 38.300

1. A method performed in a first infrastructure equipment for a handoverof a wireless communications device from the first infrastructureequipment as a source to a second infrastructure equipment as a target,the method comprising maintaining a mapping between a plurality ofpacket bearers and a data radio bearer for the wireless communicationsdevice, each of the plurality of packet bearers being configured toprovide a specified quality of service, determining that the wirelesscommunications device should handover from the first infrastructureequipment to the second infrastructure equipment, determining that thesecond infrastructure equipment does not support the mapping of theplurality of packet bearers to the data radio bearer, and providing anindication of a mapping of the plurality of packet bearers for thesecond infrastructure equipment after handover to one of a core networkequipment and the second infrastructure equipment for configuration ofat least one of the radio bearer and the plurality of packet bearers atthe second infrastructure equipment after the handover.
 2. A method asclaimed in claim 1, wherein the providing an indication of a mapping ofthe plurality of packet bearers for the second infrastructure equipmentafter handover includes providing an indication of the mapping betweenthe plurality of packet bearers and the data radio bearer for thewireless communications device maintained by the first infrastructuredevice.
 3. A method as claimed in claim 1, the method comprising:receiving from the core network equipment an indication of a mapping ofthe plurality of packet bearers to one or more packet bearers for thesecond infrastructure equipment after handover, and wherein theproviding an indication of a mapping of the plurality of packet bearersfor the second infrastructure equipment after handover includesproviding an indication of the mapping from the plurality of packetbearers to the one or more packet bearers for the second infrastructureequipment after handover.
 4. A method as claimed in claim 1, wherein theproviding the indication of the required mapping of the plurality ofpacket bearers to a corresponding plurality of data radio bearers forthe second infrastructure equipment after handover includes generating asignalling message for transmission to the core network equipment towhich the first infrastructure equipment is connected, the signallingmessage indicating that the second infrastructure equipment does notsupport the mapping of the plurality of packet bearers to the data radiobearer, and sending the signalling message to the core network equipmentin preparation for the handover.
 5. A method as claimed in claim 4wherein the signalling message provides an indication of the mapping ofa plurality of radio bearers to the plurality of packet bearers forconfiguring the second infrastructure equipment via an interface betweenthe second infrastructure equipment and a second core network to whichthe second infrastructure equipment is connected.
 6. A method as claimedin claim 1, wherein the providing the indication of the mapping of theplurality of packet bearers for the second infrastructure equipmentafter handover includes generating a transparent container fortransmission to the second infrastructure equipment, the transparentcontainer including a representation of the mapping, and transmittingthe transparent container to the second infrastructure equipment.
 7. Amethod as claimed in claim 4, wherein the transparent container istransmitted to the second infrastructure equipment from the firstinfrastructure equipment via an interface between the firstinfrastructure equipment and the second infrastructure equipment.
 8. Amethod performed in a first infrastructure equipment not supporting amapping of a plurality of packet bearers to a data radio bearer for ahandover of a wireless communications device from a secondinfrastructure equipment as a source to the first infrastructureequipment as a target, the method comprising receiving a request for thehandover of the wireless communication device, receiving an indicationof a mapping of a plurality of packet bearers for configuration of atleast one of a radio bearer and a plurality of packet bearers after thehandover, configuring a radio bearer for the wireless communicationsdevice based on the indication of the mapping of the plurality of packetbearers, generating a message indicating the configuration of thereserved radio bearer for transmission to the wireless communicationdevice.
 9. A method of claim 8, wherein the message indicating theconfiguration of the reserved radio bearer for transmission to thewireless communication device includes a mapping between the radiobearer and a packet bearer.
 10. A method of claim 8, wherein the messageindicating the configuration of the reserved radio bearer fortransmission to the wireless communication device includes a mappingbetween the radio bearer and at least one of the plurality of packetbearers.
 11. A method of claim 9, wherein the mapping between the radiobearer and at least one of the plurality of packet bearers is a mappingof all of the plurality of packet bearers to the radio bearer.
 12. Amethod of claim 8 wherein the indication of a mapping of a plurality ofpacket bearers for configuration of at least one of a radio bearer and aplurality of packet bearers after the handover is received in atransparent container generated by the second infrastructure equipment.13. A method of claim 12, comprising determining that the transparentcontainer does not comply with one or more predetermined requirements,and responsive to the determination, configuring the radio bearerwithout regards to a configuration of a radio bearer by the secondinfrastructure equipment.
 14. An infrastructure equipment forming aradio network part of a wireless communications network, configured totransmit data to and/or receive data from a wireless communicationsdevice, and to transmit the data to or receive the data from a corenetwork part of the wireless communications network, the infrastructureequipment comprising receiver circuitry configured to receive radiosignals transmitted by the wireless communications device via a wirelessaccess interface, transmitter circuitry configured to transmit radiosignals to the wireless communications device via the wireless accessinterface, and controller circuitry configured to control thetransmitter circuitry and the receiver circuitry to transmit data to orreceive data from the wireless communications device and to transmit thedata to or receive the data from the core network via an interface withthe core network, wherein the controller circuitry is configured to tomaintain a mapping between a plurality of packet bearers and a dataradio bearer for the wireless communications device, each of theplurality of packet bearers being configured to provide a specifiedquality of service, to determine that the wireless communications deviceshould handover from the first infrastructure equipment to a secondinfrastructure equipment, to determine that the second infrastructureequipment does not support the mapping of the plurality of packetbearers to the data radio bearer, and the controller is configured incombination with the transmitter circuitry to transmit an indication ofa mapping of the plurality of packet bearers for the secondinfrastructure equipment after handover to the core network equipmentfor configuration of at least one of the radio bearer and the pluralityof packet bearers at the second infrastructure equipment after thehandover.
 15. An infrastructure equipment forming a radio network partof a wireless communications network, configured to transmit data toand/or receive data from a wireless communications device, and totransmit the data to or receive the data from a core network part of thewireless communications network, the infrastructure equipment comprisingreceiver circuitry configured to receive radio signals transmitted bythe wireless communications device via a wireless access interface,transmitter circuitry configured to transmit radio signals to thewireless communications device via the wireless access interface, andcontroller circuitry configured to control the transmitter circuitry andthe receiver circuitry to transmit data to or receive data from thewireless communications device and to transmit the data to or receivethe data from the core network via an interface with the core network,wherein the controller circuitry is configured to receive a request fora handover of the wireless communication device, to receive anindication of a mapping of a plurality of packet bearers forconfiguration of at least one of a radio bearer and a plurality ofpacket bearers after the handover, to configure a radio bearer for thewireless communications device based on the indication of the mapping ofthe plurality of packet bearers and to generate a message indicating theconfiguration of the reserved radio bearer for transmission to thewireless communication device, wherein the infrastructure equipment doesnot support a mapping of a plurality of packet bearers to a data radiobearer. 16.-30. (canceled)
 31. A communications device configured totransmit radio signals to and/or receive radio signals from a firstinfrastructure equipment and a second infrastructure equipment of awireless communications network, the communications device comprising areceiver circuit configured to receive radio signals transmitted by thefirst and second infrastructure equipment via a wireless accessinterface, a transmitter circuit configured to transmit radio signals tothe first and second infrastructure equipment via the wireless accessinterface, and a controller circuit configured to control thetransmitter circuit and the receiver circuit to transmit data to orreceive data from the wireless communications network via the first andsecond infrastructure equipment, wherein the controller circuit isconfigured to control the receiver circuit to receive first data in afirst network cell from the first infrastructure equipment, the firstdata comprising a first data portion received by the firstinfrastructure equipment from a first core network and a first protocolheader in accordance with a first protocol and a second protocol headerin accordance with a second protocol, the second protocol headerincluding a sequence number, the first and second protocol headers beinggenerated by the first infrastructure equipment, to perform a handoverto a second cell associated with the second infrastructure equipment,the second infrastructure equipment connected to a second core networkdifferent from the first core network, to receive a second data in thesecond network cell, the second data comprising a second data portion,the controller configured to determine whether the second data includesa third protocol header in accordance with the first protocol, and, ifthe second data includes the third protocol header in accordance withthe first protocol, to remove the third protocol header beforeprocessing the second data in accordance with the second protocol; andthe controller circuit is configured to control the receiver circuit toreceive third data in the second network cell, the third data comprisinga third data portion received by the second infrastructure equipmentfrom the second core network and a header in accordance with the secondprotocol, the second protocol header including a sequence numbergenerated by the second infrastructure equipment.
 32. A communicationsdevice as claimed in claim 31, wherein the second infrastructureequipment is an eNodeB connected to an enhanced packet core, EPC,network and the second data has been received by the secondinfrastructure equipment from a 5G core network.
 33. A communicationsdevice as claimed in claim 31, wherein the second protocol is associatedwith a radio bearer and provides one or more of header compression,security, and retransmission of the second data.
 34. A communicationsdevice as claimed in claim 33, wherein the second protocol is a packetdata convergence protocol (PDCP).
 35. (canceled)
 36. A communicationsdevice as claimed in claim 31, wherein the first data comprises aninternet protocol, IP, packet.
 37. A communications device as claimed inclaim 31, wherein the first protocol provides a mapping of a pluralityof packet bearers, configured to provide a specified quality of service,to a data radio bearer.